Flow stress and work-hardening behaviour of Al–Mg binary alloys

•We carry out studies of mechanical properties and work hardening behaviour of Al–Mg binary alloys at 4 K, 78 K and 298 K.•The work hardening behaviour follows Voce type law at three temperatures.•The dislocation mean slip distance correlates to the scale of the cell-like dislocation network.•We analyze the relationship between the work hardening and the limits of plasticity.•The failure represents a transition in a defect-saturated microstructure at the limit of its mechanical stability.

Analysis of the flow stress and work hardening behaviour has been carried out in series of Al–Mg solid solutions between 4 K and 298 K. The results reveal that the yield stress decreases linearly with the temperature and increases approximately linearly with the Mg content in the solution. The thermomechanical and Portevin–Le Chatelier instabilities dominate the flow stress behaviour of alloys at 4 K and 298 K. Dynamics of these instabilities increases with the solute content. It is argued that neither PLC nor adiabatic instabilities contribute to the premature failure of the samples. The work-hardening can be reproduced by the Voce type scaling law in a broad range of temperatures. The mean slip distance obtained from the macroscopic model of work hardening is correlated to the scale of the referenced microstructure; ΛminΛmin is interpreted as a transition from cell-like to micro shear band microstructure. The failure is discussed in terms of a critical point in a transition form unsaturated to saturated with defects dislocation substructure.